用XANES方法研究SO2在超细Fe3O4颗粒表面的非均相反应

摘要

超细颗粒物为大气中痕量气态污染物转化提供了广泛的反应界面,在其表面发生多相界面反应是大气二次颗粒物形成的主要途径.含铁超细颗粒是大气气溶胶的主要成分之一.本研究采用同步辐射X射线近边吸收谱(X-ray Absorption Near Edge Structure, XANES)技术开展了Fe3O4超细颗粒表面的多相反应研究,分析了反应时间、紫外照射及臭氧存在条件对二次颗粒物形成的影响.研究发现:SO2在Fe3O4超细颗粒表面能被快速氧化形成硫酸根(SO42?),其中紫外光照(Ultra-Violet, UV)和 O3可以促进硫酸根的生成.从反应时间上看, SO2在Fe3O4超细颗粒表面可快速反应生成高价态硫酸根,30 min时,约99%的硫化物转化成硫酸根.通过对S的XANES谱进行一阶导数处理,发现产物中还存在亚硫酸根(SO32?)的峰,提示SO2在Fe3O4颗粒物表面可先生成亚硫酸根,进而被快速氧化成硫酸根.%[Background] Ultrafine particles (UFPs) may provide various micro-locations of heterogeneous chemical reactions of trace of gaseous substances in atmospheric environment. Iron-containing UFPs are the main components of atmospheric aerosol. [Purpose] This study aims to investigate heterogeneous reactions of SO2on Fe3O4UFPs.[Methods] S K-edge of products was investigated by synchrotron radiation X-ray absorption near edge structure (XANES). [Results] The results indicated that SO2could be rapidly oxidized to form sulfate on the surface of Fe3O4. Formation of sulfate can be promoted under the UV and O3conditions. [Conclusion] The formation of adsorbed sulfate likely involves the formation of pre-absorbed sulfite (SO32?) and subsequent oxidation.